CfA Safety: Compressed Gases
 

Intent: To inform supervisors and users of compressed gases of the safety procedures for working with inert, flammable, pyrophoric, oxidizing, corrosive and toxic gases.

Information: Compressed gases have the potential to create both chemical and mechanical hazards if handled, transported or stored improperly. The unique hazards presented by compressed gases are dependent upon their physical and chemical properties and the pressure of the gas in a cylinder or delivery system.

The various types of compressed gases are described as follows:

  • Nonflammable (Inert) Gas - a non reactive gas which is not considered to be hazardous unless uncontrollably released into an enclosed area. Inert gases may cause asphyxiation under these conditions. Nonflammable gases should be labeled as "nonflammable gas" on a green and white placard.
  • Flammable Gas - a gas which may be ignited or explode when it accumulates between the lower and upper explosive limits for a specific gas. Safety precautions are required when handling, using and storing flammable gases. Flammable gases should be labeled as "flammable gas" on a red and white placard.
  • Pyrophoric Gas - a highly flammable and reactive gas which may spontaneously burn or explode when released into air. Special safety precautions are required when handling, using and storing pyrophoric gases due to their reactivity. Pyrophoric gases should be labeled as "flammable gas" on a red and white placard.
  • Oxidizing Gas (e.g. oxygen) - a gas which may promote the rapid combustion or reactivity of flammable gases or materials. These gases should not be stored or mixed uncontrollably with flammable gases due to their fire or explosive hazard. Oxidizing gases are labeled as "oxidizer" on a yellow and black placard.
  • Corrosive Gas - a reactive gas which may degrade materials and cause permanent damage to body tissues upon direct contact. Special safety precautions are required when handling, using and storing corrosive gases. Corrosive gases are often labeled as "poison" on a white and black placard.
  • Toxic Gas - a highly poisonous gas which may be immediately dangerous to life and health if accidentally released. Special safety precautions are required when handling, using and storing toxic gases due to their extreme toxicity. Toxic gases should be labeled as "poison gas" on a white and black placard.

Standard: The following safety procedures are required when handling, using and storing all compressed gases. Additional special safety precautions have been developed for corrosive, pyrophoric and toxic gases.

Supervisors and users of compressed gases must ensure the following general precautions are followed:

  • Compressed gas cylinders must be clearly labeled by a shipment tag or stenciled name at all times. Gas cylinders without labels should not be accepted. Color coding is not a reliable means of identification. Unidentified cylinders should be returned to the supplier.
  • Compressed gas cylinders must be firmly secured at all times. An appropriate clamp, belt or chain should be used for this purpose.
  • The cylinder valve cap must be secured on the head of a cylinder whenever it is not in use. This protects the vulnerable cylinder valve and prevents the cylinder from becoming a dangerous projectile in the event of an accident. Never lift a cylinder by the valve cap.
  • All compressed gas cylinders should be inspected upon their receipt. Damaged or unidentified cylinders should be immediately returned to the supplier.
  • Only CGA standard combinations of valve and fittings should be used on compressed gas systems. This reduces the possibility of accidentally mixing incompatible gases due to an interchange of connections. The threads and conditions of cylinder valves, regulators and fittings should be examined to ensure they are undamaged and correspond to one another.
  • Compressed gas cylinders should only be handled, used or stored in locations where they are not exposed to elevated temperatures, pressures or voltages. Cylinders should not be allowed to become part of an electrical circuit.
  • Only appropriate tools should be used on gas valves and piping systems. Improper tools may damage or exert unacceptable stresses on a compressed gas system.
  • Cylinder valves should be opened slowly to prevent "over-stressing" compressed gas systems.
  • Only matched components should be used on compressed gas systems. The materials of construction, design and installation of individual components is very important to the safe use of gas systems.

  • Rigid piping is required for the construction of all permanent gas systems. Flexible tubing may only be used in limited instances on nonflammable (inert) gas systems.
  • All compressed gas systems must be treated after their construction and prior to their use. Gas systems should be over-pressurized with an inert gas to ensure their integrity. Gas systems should have a dedicated cylinder of inert gas for purging. The house nitrogen, vacuum and compressed gas must not be used to purge regulators or systems for flammable, pyrophoric, oxidizing, corrosive and toxic gases.
  • Employees storing, using and handling compressed gases should understand the properties, hazards and safety precautions by consulting their supervisors, Material Safety Data Sheets or other references.
  • All flammable and oxidizing gases should be stored separately. Flammable gases and oxygen should never be stored in close proximity to each other or within the same ventilated gas cabinet.
  • All flammable, pyrophoric, corrosive and toxic gases should be delivered to users after working hours. Users of these gases should arrange with building service personnel to receive and store their gases inside secured ventilated cabinets. Cylinders of hazardous gases should never be left in hallways, aisles or unprotected in labs without the knowledge of the occupant.
  • All gas cylinders should be secured to an appropriate hand truck when transported through hallways or moved within a laboratory. Gas cylinders should be transported cautiously to prevent personal injury or damage to the cylinder.
  • Gas monitoring devices should be installed in labs where flammable, pyrophoric, corrosive and toxic gases are stored, handled or used. Monitoring devices should be interlocked with gas systems to cut the flow of gas if a leak is detected. Questions concerning the purchase of gas monitoring devices or air sampling to assess potential exposure to gas should be raised with the CfA Safety Office.
  • The quantities of flammable, pyrophoric, toxic, corrosive, and oxidizing gases should be kept to the minimum needed for an operation. Stockpiling of gases in laboratories or shops is not permitted.

Contact: Whenever questions arise about the safe handling, use and storage of compressed gases, contact the CfA Safety Office at 5-7478.

 
 

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